This invention pertains to weighing apparatus for a fifth wheel assembly.
Fifth wheel assemblies are used in many applications to couple a trailer to a tractor. The assembly, in such an instance, is normally mounted on and adjacent the rear end of the frame in a tractor.
There are a number of instances in which it is desirable to be able to measure the load transmitted into a tractor frame through such an assembly. For example, in vehicles which are used to haul especially heavy loads, it is important that the overall weight of a loaded vehicle be held below certain statutory maximum limits. With these kinds of vehicles, an onboard scale (or weighing) system offers a significant advantage to a vehicle operator, in that he can instantly monitor the loaded condition of his vehicle a loading operation.
A general object of the present invention is to provide a unique, simple, accurate and reliable system for weighing the load transmitted through a fifth wheel assembly provided for coupling a tractor and trailer.
According to a preferred embodiment of the invention the proposed scale apparatus includes a rockable subframe adapted for carrying a conventional fifth wheel assembly, with this subframe constructed for pivotal mounting with respect to an underlying vehicle frame. An inflatable air pad is disposed beneath the subframe, and is operable, under inflation, to pivot and lift the subframe to a position wherein the pad carries a portion of any load borne by the subframe. Connected to the pad is a calibrated air scale system for producing an appropriate load indication. Further provided in the apparatus is a safety lock mechanism for releasably locking the subframe against pivoting under conditions of normal vehicle travel.
When it is desired to weigh the load carried through a fifth wheel assembly, this is normally done with the vehicle stationary. The lock mechanism is operated to release the subframe, and the air pad is inflated to pick up and pivot the subframe, thereby itself beginning to carry a part of the load transmitted into the subframe. Under this circumstance, a load reading may be taken, and of course the scale system will have been precalibrated so as to provide a direct indication of load on the associated fifth wheel assembly.
When weighing is complete, and it is desired to prepare the vehicle for travel, the air pad is deflated to relower the subframe, and the lock mechanism is reactuated to lock the subframe securely in place. As a consequence of this action the fifth wheel assembly carried on the subframe is secured with respect to a tractor's frame, and, during travel, dynamic and static loads are not required to be carried through the air pad.
These and other objects and advantages which are attained by the invention, will become more fully apparent as the description which now follows is read in conjunction with the accompanying drawings.